The present invention relates to a fuel pump for supplying fuel to an internal combustion engine, particularly relates to a high pressure fuel pump used in a fuel injection system of so-called in-cylinder direct injection type of an internal combustion engine, the system directly injects fuel into a fuel chamber through a fuel injection valve attached to the fuel chamber.
A type of system which directly injects fuel to a combustion chamber of an internal combustion engine requires a high pressure fuel pump for increasing a pressure of fuel to be supplied to a fuel injection valve up to the pressure of 3 MPa or higher.
Such a high pressure pump has been known from JP-A-9-236080 as an axial plunger pump. Conventionally, such a high pressure pump is configured so as to part a driving mechanism part lubricated with oil from a pump chamber compressing and discharging fuel by metal bellows.
Another conventional high pressure fuel pump is described in JP-A-9-250447. The pump is configured so as to circulate fuel up to the sliding part of the driving mechanism part, in the other word, lubricate the driving mechanism part with fuel. In this prior art, the sliding part is lubricated with fuel.
Such types of conventional high pressure pump have problems as follows;
(1) As for the former pump, the pomp has a large sized shape by using the metal bellows. In addition, the pump needs a sealing part at a mounting part of the bellows. Because of these points, the pump has a problem that it is difficult to miniaturize the pump.
(2) As for the latter pump, the bellows is not necessary. However, a lubricating condition of the driving mechanism part is hard since the sliding part is lubricated with fuel of a low viscosity.
The object of the present invention is to provide an axial plunger pump which does not need bellows and lubricates the driving mechanism part sufficiently.
Another object of the present invention is to allow the pump to use a rolling bearing for the driving mechanism.
In order to solve the problems, the present invention provides a high pressure fuel pump comprising a cup-shaped body; a cylinder block engaged with the cup-shaped body so as to close the opening side of the cup-shaped body; a rotation shaft supported at the bottom of the cup-shaped body and rotated by a driving source; a swash plate disposed in a driving mechanism chamber inside the cup-shaped body, which converts a rotating movement to a shaking movement; a plunger reciprocated in a cylinder bore formed in the cylinder block according to the shaking movement of the swash plate; a sealing element provided between the inside wall of the cylinder bore and the plunger; and an oil supply mechanism which supplies oil to the driving mechanism chamber.
According to further aspect of the present invention, it provides a high pressure fuel pump comprising: a cup-shaped body; a cylinder block engaged with the cup-shaped body so as to close the opening side of the cup-shaped body; a rotation shaft supported at the bottom of the cup-shaped body and rotated by a driving source; a swash plate disposed in a driving mechanism chamber inside the cup-shaped body, which converts a rotating movement to a shaking movement; a plunger reciprocated in a cylinder bore formed in the cylinder block according to the shaking movement of the swash plate; a sealing element provided between the inside wall of the cylinder bore and the plunger; an oil supply mechanism which supplies oil to the driving mechanism chamber; a low pressure side fuel passage formed in the cylinder block; and a low pressure fuel introducing passage formed in the plunger, which connects the low pressure side fuel passage with a pump chamber formed in the cylinder bore, the pump chamber varying its capacity according to the plunger reciprocating in the cylinder bore.
Moreover, the high pressure fuel pump may comprise a valve mechanism disposed between the low pressure side fuel passage and the pump chamber, which shut off the connection between the low pressure side fuel passage and the pump chamber when a pressure of the pump chamber is more than a defined pressure so that the sealing element is adopted to be acted by a pressure of the upper stream of the valve mechanism.
According to another aspect of the present invention, it provides 9 a high pressure fuel pump comprising: a shaft for transmitting a driving force from the outside; a cam converting a rotating movement of the shaft to a reciprocating movement; a plunger reciprocated by the cam; a cylinder bore formed in a cylinder block; a pump chamber formed by putting the plunger into the cylinder bore; a sealing element sealing a apace between the cylinder bore and the plunger; and an oil supply mechanism which supplies oil to the cam.